Replace atty by std::io::IsTerminal

[atezet]

Changes

atty is now unmaintained RUSTSEC-2024-0375. Replaced the only occurrence with std::io::IsTerminal.

Checklist

• An issue to be fixed by this PR is listed above.
• [-] New tests are added to ensure new features are working. Please refer to this page to see how to add a test.
• ./frb_internal precommit --mode slow (or fast) is run (it internal runs code generator, does auto formatting, etc).
• [-] If this PR adds/changes features, documentations (in the ./website folder) are updated.
• CI is passing. Please refer to this page to see how to solve a failed CI.

Remark for PR creator

• ./frb_internal --help shows utilities for development.
• If fzyzcjy does not reply for a few days, maybe he just did not see it, so please ping him.

[fzyzcjy]

LGTM and thanks!

To make CI happy, I guess you can either (1) revert the changes to pubspec.lock (2) or use the same Flutter version as CI's. Feel free to ping me after CI is green to merge it :)